This invention relates to wall elements for gas turbine engine combustors.
A typical gas turbine engine combustor includes a generally annular chamber having a plurality of fuel injectors at an upstream head end. Combustion air is provided through the head and in addition through primary and intermediate mixing ports provided in the combustor walls, downstream of the fuel injectors.
In order to improve the thrust and fuel consumption of gas turbine engines, i.e. the thermal efficiency, it is necessary to use high compressor pressures and combustion temperatures. Higher compressor pressures give rise to higher compressor outlet temperatures and higher pressures in the combustion chamber.
There is, therefore, a need to provide effective cooling of the combustion chamber walls. One cooling method which has been proposed is the provision of a double walled combustion chamber, in which the inner wall is formed of a plurality of heat resistant tiles. Cooling air is directed into the gap between the outer wall and the tiles, and is then exhausted into the combustion chamber.
The tiles can be provided with a plurality of pedestals which assist in removing heat from the tile. However, it has been found that certain parts of the tile are still prone to overheating and subsequent erosion by oxidation.
According to one aspect of this invention, there is provided a wall element for a wall structure of a gas turbine engine combustor, the wall element including at least one surface, the surface, in use, faces in a downstream direction relative to the general direction of fluid flow through the combustor, wherein said surface comprises a thermally resistant material.
The wall element preferably includes a main body member, the main body member comprising upstream and downstream edges. The downstream edge preferably comprise a downstream facing surface, the downstream facing surface comprising said thermally resistant material. The wall element may have a plurality of upstanding heat removal members provided on the main body member. Each heat removal member furthest downstream on the main body member may comprise the thermally resistant material. The heat removal members may have a substantially circular cross-section.
The wall element preferably comprises a tile. The heat removal members are preferably heat removal pedestals. Advantageously, the thermally resistant material extends substantially the whole length of the heat removal member or members.
The thermally resistant material may be a coating, suitably a thermal barrier coating, for example magnesium zirconate or yttria stabilized zirconia.
In one embodiment, the heat removal members are substantially cylindrical in configuration, the surface of the, or each, member provided with said thermally resistant material comprising a downstream facing arc. Preferably said arc subtends an angle of at least substantially 90xc2x0, and more preferably substantially 180xc2x0. Preferably the angle subtended by said arc is no more than substantially 180xc2x0.